derivative calculator

calculators operate in digital numbers
the derivative is a numeric proportion or rate
calculators can specify derivatives by digital numbers

By adding another number to each precise-real number -
infinitesmals, rather than complex imaginary-parts -
we can have calculators compute derivatives:
the second number is the slope at the precise-real number,
thus sin(pi/2) = 1.0000000000 ,
and its second number, its derivative, is 0.0000000000 = cos(pi/2) .